JP6597197B2 - Beam diameter expanding element and display device - Google Patents

Description

  The present invention relates to a light beam diameter enlarging element for enlarging a light beam diameter and a display device including the light beam diameter enlarging element.

  In a retinal scanning display device in which a light-modulated light beam is incident on the user's eye, if the light beam diameter is small, the light beam does not enter the pupil when the position of the pupil changes. End up. In view of this, a retinal scanning display device is provided with a beam diameter enlarging element (pupil enlarging element). As a light beam diameter expanding element, for example, an element in which a diffraction grating is provided on each of two opposing surfaces of a light guide plate, the grating periods of the both are the same, and the diffraction angles are matched is proposed (Patent Document 1, Patent Document 1). 2). In Patent Document 1, two diffraction gratings face each other, and both + 1st order diffracted light and −1st order diffracted light are used. In Patent Document 2, two diffraction gratings are separated in the extending direction of the light guide plate, and one of + 1st order diffracted light and −1st order diffracted light is used.

JP-A-7-72422 JP 2007-219106 A

  In the light beam diameter enlarging element described in Patent Document 1, light diffracted by the incident-side diffraction grating is directly emitted from the emission-side diffraction grating. For this reason, since the light beam diameter is only enlarged by the amount corresponding to the diffraction angle of the diffraction grating, it is difficult to greatly enlarge the light beam diameter. On the other hand, in the light beam diameter enlarging element described in Patent Document 2, the diffracted light diffracted by the incident side diffraction grating is emitted from the output side diffraction grating while being reflected inside the light guide plate. Can be enlarged. However, since the light beam diameter enlarging element described in Patent Document 2 uses a volume phase type holographic diffractive optical element, incident light is diffracted and used only in a specific direction, so that the light beam is emitted only on one side. Can not be expanded. Therefore, since the size of the diffraction grating on the incident side is required in addition to the size of the diffraction grating on the output side, there is a problem that the size of the beam diameter expanding element is increased.

  In view of the above problems, an object of the present invention is to provide a light beam diameter expanding element and a light beam diameter expanding element capable of greatly expanding the light beam diameter while suppressing an increase in the size of the light beam diameter expanding element. It is to provide a display device provided.

  In order to solve the above-described problem, an aspect of the light beam diameter expanding element according to the present invention includes a first light guide plate having a first surface and a second surface that is a surface opposite to the first surface, A first incident-side diffraction grating provided on the first surface; and a first emission-side diffraction grating provided on the second surface, wherein the first surface is parallel to the second surface. The first incident-side diffraction grating and the first emission-side diffraction grating are provided so that the grating directions are the same and the grating period is the same, and the refractive index of the first light guide plate Is a refractive index such that the diffraction angle of the + 1st order diffracted light and the diffraction angle of the −1st order diffracted light of the first light beam incident on the first incident side diffraction grating are respectively greater than or equal to the critical angle. When the direction intersecting the grating direction of the incident side diffraction grating is the first direction, the first incident side diffraction grating The folded first-order diffracted light and first-order diffracted light of the first light propagate in the first light guide plate in directions opposite to each other in the first direction and are emitted from the first emission-side diffraction grating. It is characterized by.

  In the present invention, since the + 1st order diffracted light and the −1st order diffracted light diffracted by the first incident side diffraction grating are propagated in directions opposite to each other in the first direction of the light guide plate and emitted from the first exit side diffraction grating, the beam diameter is The light is emitted from the first emission side diffraction grating in a sufficiently enlarged state. Therefore, it is possible to suppress an increase in the size of the light beam diameter expanding element, and the light use efficiency is high. In addition, since the diffraction angle of the + 1st order diffracted light and the diffraction angle of the −1st order diffracted light of the first light beam are equal to or larger than the critical angle defined by the refractive index of the first light guide plate, the light guide plate is totally reflected. Because it propagates through, the light utilization efficiency is high.

  In one aspect of the light beam diameter expanding element according to the present invention, a third surface is provided so as to face the second surface of the first light guide plate, and a fourth surface is provided on the side opposite to the third surface. A second light guide plate, a second incident-side diffraction grating provided on the third surface, and a second output-side diffraction grating provided on the fourth surface, wherein the third surface comprises the first The second incident side diffraction grating and the second emission side diffraction grating are provided so as to have the same grating direction and the same grating period. The grating direction of the second incident side diffraction grating is provided so as to be the same as the grating direction of the first incident side diffraction grating, and the grating period of the second incident side diffraction grating is the first incident side diffraction grating. The second light guide plate has a refractive index different from that of the first light beam and a wavelength. Refractive index so that the diffraction angle of the + 1st order diffracted light and the diffraction angle of the −1st order diffracted light of the second light ray when the different second light rays are incident on the second incident-side diffraction grating are respectively greater than the critical angle. The + 1st order diffracted light and the −1st order diffracted light of the second light beam diffracted by the second incident side diffraction grating propagate in the second light guide plate in directions opposite to each other in the first direction. The light is preferably emitted from the second emission side diffraction grating.

  In one aspect of the light beam diameter expanding element according to the present invention, a fifth surface is provided so as to face the fourth surface of the second light guide plate, and a sixth surface is provided on the side opposite to the fifth surface. A third light guide plate; a third incident-side diffraction grating provided on the fifth surface; and a third output-side diffraction grating provided on the sixth surface. The third entrance-side diffraction grating and the third exit-side diffraction grating are provided so that the grating directions are the same and the grating period is the same period. The grating direction of the third incident side diffraction grating is provided to be the same as the grating direction of the first incident side diffraction grating, and the grating period of the third incident side diffraction grating is the first incident side diffraction grating. And having a period different from the grating period of the second incident side diffraction grating, The refractive index is determined by the diffraction angle of the + 1st order diffracted light and the -1st order diffracted light of the third light beam when a third light beam having a wavelength different from that of the first light beam and the second light beam is incident on the third incident side diffraction grating. The third light guide plate has a refractive index such that a diffraction angle is equal to or greater than a critical angle, and the + 1st order diffracted light and the −1st order diffracted light of the third light diffracted by the third incident side diffraction grating are the third light guide plate. It is preferable that the light propagates in directions opposite to each other in the first direction and is emitted from the third emission side diffraction grating.

In one aspect of the light beam diameter expanding element according to the present invention, the grating period of the first incident side diffraction grating is P1, the grating period of the second incident side diffraction grating is P2, and the grating of the third incident side diffraction grating is When the period is P3, the grating periods P1, P2, and P3 have the following relationship: P1 <P2 <P3
Is preferably satisfied. According to such a configuration, when the wavelengths of the first light beam, the second light beam, and the third light beam have the following relationship: first light beam <second light beam <third light beam, the emission intervals of the respective light beams can be aligned, The amount of emitted light and the uniformity of color can be improved.

In another aspect of the light beam diameter expanding element according to the present invention, the grating height of the first incident-side diffraction grating is H11, the grating height of the second incident-side diffraction grating is H21, and the third incident-side diffraction is performed. When the lattice height of the lattice is H32, the lattice heights H11, H21, and H31 have the following relationship: H11 <H21 <H31
Is preferably satisfied. According to this configuration, when the wavelengths of the first light beam, the second light beam, and the third light beam have the following relationship: first light beam <second light beam <third light beam, the first-order diffraction efficiency of the light beam handled by each light guide plate is In addition to providing a bright beam expanding element, unnecessary diffracted light can be suppressed.

In another aspect of the light beam diameter expanding element according to the present invention, the grating height of the first exit side diffraction grating is H12, the grating height of the second exit side diffraction grating is H22, and the third exit side diffraction is performed. When the lattice height of the lattice is H32, the lattice heights H11, H12, H21, H22, H31, and H32 have the following relationship: H12 <H11 <H22 <H21 <H32 <H31
Is preferably satisfied. According to such a configuration, since the light is dispersed and emitted from the diffraction grating on the emission side, the light quantity distribution in the emission light can be optimized.

In still another aspect of the light beam diameter expanding element according to the present invention, a grating period of the first incident-side diffraction grating and the first emission-side diffraction grating is P, and the shortest wavelength in the half-value width of the spectrum of the first light beam is When λc and the maximum incident angle of the first light ray with respect to the first incident-side diffraction grating is θmax, the grating period P, the shortest wavelength λc, and the maximum incident angle θmax have the following relationship: P ≦ λc / [sin (θmax +1]
Is preferably satisfied.

  One aspect of a display device including a light beam diameter enlarging element to which the present invention is applied includes an image generation device and a collimator lens, and image light generated by the image generation device is transmitted through the collimator lens through the light beam diameter. An image light projection device that is incident on the magnifying element, and a light guide optical system that guides the image light emitted from the light beam diameter magnifying element in a second direction that intersects the first direction.

  In one aspect of the display device according to the present invention, it is preferable that an exit pupil in the image light projection device is located between an entrance surface and an exit surface of the light beam diameter enlarging element.

  In one aspect of the display device according to the present invention, it is preferable that the exit pupil is located between the entrance surface and the exit surface of the beam diameter expanding element.

  In another aspect of the display device according to the present invention, it is preferable that the size of the light beam diameter enlarging element in the first direction is smaller than the size of the light guide optical system in the first direction. With this configuration, the display device can be reduced in size.

  In still another aspect of the display device according to the present invention, it is possible to adopt a configuration in which the first direction is a vertical direction in the display device, and the second direction is a horizontal direction in the display device.

  In still another aspect of the display device according to the present invention, the first direction may be a horizontal direction in the display device, and the second direction may be a vertical direction in the display device.

It is explanatory drawing which shows the one aspect | mode of the light beam diameter expansion element which concerns on Embodiment 1 of this invention. It is explanatory drawing when image light injects into the light beam diameter expansion element shown in FIG. It is explanatory drawing which shows the specific structural example of the light beam diameter expansion element which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the one aspect | mode of the light beam diameter expansion element which concerns on Embodiment 2 of this invention. It is explanatory drawing when blue light injects into the light guide plate for blue used for the beam diameter expansion element shown in FIG. It is explanatory drawing when green light injects into the light guide plate for green used for the beam diameter expansion element shown in FIG. It is explanatory drawing when the red light L injects into the light guide plate for red used for the light beam diameter expansion element shown in FIG. It is explanatory drawing which shows the one aspect | mode of the light beam diameter expansion element which concerns on Embodiment 3 of this invention. It is explanatory drawing which shows the structural example of the display apparatus provided with the light beam diameter expansion element to which this invention is applied. It is explanatory drawing which shows the optical system of the display apparatus shown in FIG. It is explanatory drawing of the exit pupil of the optical system shown in FIG. It is explanatory drawing which shows another structural example of the display apparatus provided with the light beam diameter expansion element to which this invention is applied.

  Embodiments of the present invention will be described below. In the drawings to be referred to in the following description, the scales are different for each layer and each member so that each layer and each member have a size that can be recognized on the drawing. In the following description, the direction in which the grating of the diffraction grating extends is the x direction, the direction perpendicular to the x direction is the y direction, and the direction perpendicular to the x direction and the y direction is the z direction. Will be described. Therefore, the “first direction” in the present invention corresponds to the x direction, and the diffraction direction by the diffraction grating (“second direction”) corresponds to the y direction.

[Embodiment 1]
(Basic configuration)
FIG. 1 is an explanatory view showing an aspect of a light beam diameter expanding element according to Embodiment 1 of the present invention. FIG. 2 is an explanatory diagram when image light is incident on the beam diameter enlarging element shown in FIG. 1 and 2, C11 is shown on the left side of the drawing when the light with the wavelength λc is incident at the incident angle + θmax, and light on the wavelength λc is on the right side of the drawing with the incident angle −θmax. C12 is shown when the light is incident at.

  As shown in FIG. 1, the luminous flux diameter expanding element 10 of this embodiment has a single light guide plate 1. In the light beam diameter expanding element 10, the light guide plate 1 corresponds to a “first light guide plate” of the present invention. The light guide plate 1 is a parallel plate of glass or optical resin having a refractive index of n, and an incident side diffraction grating 11 (first incident side diffraction grating) is formed on one surface 1a (first surface) thereof. An exit side diffraction grating 12 (first exit side diffraction grating) is formed on a surface 1b (second surface) facing in parallel with 1a. In the incident side diffraction grating 11, a plurality of gratings 11a extending in the x direction perpendicular to the paper surface are formed at equal intervals in the y direction. In the output side diffraction grating 12, a plurality of gratings 12a extending in the x direction perpendicular to the paper surface are formed at equal intervals in the y direction.

  In the light beam diameter enlarging element 10, the incident side diffraction grating 11 and the emission side diffraction grating 12 are formed in a region overlapping in the optical axis L direction. However, the exit-side diffraction grating 12 is formed in a wider area than the incident-side diffraction grating 11, and the exit-side diffraction grating 12 is opposite to the y direction from the area where the entrance-side diffraction grating 11 is formed. It is formed over a wide area. Therefore, the light beam diameter enlarging element 10 diffracts the light beam L10 (first light beam) incident from the incident side diffraction grating 11 and propagates it in the light guide plate 1 in opposite directions in the y direction, and exits from the output side diffraction grating 12. can do. Therefore, the beam diameter expanding element 10 can perform pupil expansion in the y direction of the image light composed of the light beam L10. The term “pupil enlargement” as used herein refers to obtaining a plurality of outgoing lights that are emitted from different positions at the same angle as the incident angle of the incoming light, and is a reproduction of a light beam that preserves the angle.

  In this embodiment, the incident side diffraction grating 11 and the emission side diffraction grating 12 are surface relief type diffraction gratings, and the incident side diffraction grating 11 and the emission side diffraction grating 12 have the same grating direction and grating period. By making the grating period P the same in the incident side diffraction grating 11 and the emission side diffraction grating 12, diffracted light emitted at the same angle as the incident angle can be obtained.

Here, assuming that the maximum field angle that defines the size of the screen is a half angle and θmax, the incident angle of the incident light of the image incident on the incident side diffraction grating 11 is in the range of −θmax to + θmax. In this embodiment, attention is paid to ₊ 1st order diffracted light L _{+ 1} and −1st order diffracted light L− ₁ that can increase the diffraction efficiency among the diffracted lights. Note that 0 is order diffracted light L ₀ is also occurring, it does not contribute to the pupil expander, 0 order diffraction efficiency is preferably low.

The light beam diameter enlarging element 10 of this embodiment generates a plurality of lights emitted at the same angle as the incident angle in both directions. Therefore, both the + 1st order diffracted light L ₊ 1 propagating in the + y direction and the −1st order diffracted light L− ₁ propagating in the −y direction need to propagate through the light guide plate 1 with total reflection.

In order to propagate through the light guide plate 1 by total reflection, the diffraction angles of the + 1st order diffracted light L _{+ 1} and the −th order diffracted light L− ₁ must be larger than the critical angle determined by the refractive index n of the light guide plate 1. As indicated by the case C11, the diffracted light beam L10 having an incident angle of + θmax has a smaller diffraction angle in the -1st order diffracted light L- ₁ . Therefore, if the absolute value of the diffraction angle θ ₋₁ of the _{−1st order} diffracted light L ₋₁ is larger than the critical angle θc, the diffraction angle θ + 1 of the + 1st order diffracted light L _{+ 1} is necessarily larger than the critical angle θc.

When the grating period P is constant, the diffraction angle depends on the wavelength of incident light, and the shorter the wavelength, the smaller the diffraction angle. Therefore, in the spectrum of the image light propagating through the light guide plate 1, if the absolute value of the diffraction angle θ ₋₁ of the _{−1st order} diffracted light L ₋₁ with respect to the shortest wavelength λc that effectively contributes to image display is larger than the critical angle θc. The light can be propagated in both the + y direction and the −y direction over the entire spectrum of the image light.

When the incident angle of the image light becomes −θmax, in C12, when the incident angle is changed from + θmax to −θmax, the diffraction angle θ− ₁ of the _{−1st order} diffracted light L− ₁ gradually increases in the negative direction, Propagation in the -y direction due to total reflection is maintained. On the other hand, the diffraction angle θ ₊₁ of the + 1st order diffracted light L _{+ 1} gradually decreases, but the arrangement of the light guide plate 1 and the diffraction grating is symmetric with respect to the optical axis L. As can be seen, even when the incident angle becomes −θmax, the diffraction angle θ _{+ 1} is larger than the critical angle θc. Therefore, propagation in the + y direction due to total reflection is maintained.

In the following, a condition that can be propagated by total reflection in both the + y direction and the -y direction will be described with equations. First, the wavelength of incident light (light ray L10) is λc, the incident angle is θmax, the refractive index of the light guide plate 1 is n, and the diffraction angle of the _{−1st order} diffracted light L _{−1 in} the light guide plate 1 is θ _−1. , The grating period P at which the diffraction angle θ ₋₁ coincides with the critical angle θc is expressed by the following equation.
P = λc / [sin (θmax) +1] (1)

Here, if the grating period P is smaller than the value represented by the formula (1), the diffraction angle θ ₋₁ of the _{−1st order} diffracted light L ₋₁ becomes larger than the critical angle θc. Therefore, in order to propagate the image light (light ray L10) incident on the incident side diffraction grating 11 in both the + y direction and the -y direction by total reflection, the following conditional expression should be satisfied.
P ≦ λc / [sin (θmax) +1]... (2)

On the other hand, when the grating period P is determined, the diffraction angle θm (m is the diffraction order) by the incident-side diffraction grating 11 is λ and the incident angle is θi. Desired.
θm = sin ⁻¹ {[sin (θi) + m (λ / P)] / N} (3)

  In FIG. 1, the image light is represented by a line (light ray L), but actually, as shown in FIG. 2, the image light L <b> 1 is a light beam having a spatial spread. Therefore, the size of the region where the incident side diffraction grating 11 is formed is preferably the size of the light beam of the image light L1.

(Specific configuration example)
FIG. 3 is an explanatory diagram showing a specific configuration example of the light beam diameter expanding element 10 according to Embodiment 1 of the present invention. In FIG. 3, C21 is shown on the left side of the drawing when light having the shortest wavelength λc (0.46 nm) is incident, and red on the right side of the drawing is red with the wavelength λR (0.61 nm). C22 is shown when light L (R), green light L (G) with wavelength λG (0.53 nm), and blue light L (B) with wavelength λB (0.4747 nm) are incident.

  First, based on the case 21 of FIG. 3, the grating periods of the incident side diffraction grating 11 and the emission side diffraction grating 12 are determined. In the spectrum of image light, the shortest wavelength λc necessary for image display is 0.46 μm, and the half angle + θmax of the maximum angle of view is 7 °. When the refractive index n of the light guide plate 1 is 1.64, the critical angle θc is 37.6 °. Here, it is assumed that the wavelength dependence of the refractive index n of the light guide plate 1 is extremely small.

When the grating period P of the incident side diffraction grating 11 and the emission side diffraction grating 12 is determined so that the diffraction angle θ _{−1 of the −1st order} diffracted light L ₋₁ becomes the critical angle θc, P = 0 from Equation (1). 410 μm. When light having wavelengths λR, λG, and λB is incident on the light guide plate 1 including the incident side diffraction grating 11 and the output side diffraction grating 12, the red light L (R) having the wavelength λR is incident on the incident side diffraction grating 11. Diffracted light is generated in each of the incident light of the green light L (G) having the wavelength λG and the blue light L (B) having the wavelength λB. The diffracted light propagates in the light guide plate 1 in the + y direction and the −y direction, The light is emitted from the emission side diffraction grating 12 at an emission angle of 7 °. Indicates that time +1 diffraction angle theta ₊₁ order diffracted light _{L +1} (+1 order diffraction) and -1 diffraction angle theta _-1 order diffracted light _L-1 a (-1 order diffraction) in Table 1.

  As shown in Table 1, since the absolute value of the diffraction angle exceeds the critical angle 37.6 in the light of any wavelength λR, λG, λB, the incident light (first light beam) is converted into the + y direction of the light guide plate 1 and It can be propagated by total reflection toward both of the −y directions and can be emitted from the exit-side diffraction grating 12.

(Main effects of this form)
Thus, the beam diameter enlarging device 10 of the present embodiment, + 1st-order diffracted light _{L +1} and -1 order diffracted light _{L -1} light guide plate 1 in the y direction of a light ray L10 diffracted at the incident side grating 11 (first direction) Are propagated in the opposite directions of each other and emitted from the exit side diffraction grating 12, so that the beam diameter is emitted from the exit side diffraction grating 12 in a sufficiently enlarged state. In addition, since the incident-side diffraction grating 11 and the emission-side diffraction grating 12 are formed in a region overlapping in the optical axis L direction, it is possible to suppress an increase in the size of the light beam diameter expanding element. Further, the diffraction angle θ _{+1 of the +} 1st order diffracted light L ₊₁ of the light beam L 10 and the diffraction angle θ ₋₁ of the _{−1st order} diffracted light L ₋₁ are angles greater than the critical angle θc defined by the refractive index of the light guide plate 1. For this reason, since the + 1st order diffracted light L _{+ 1} and the −1st order diffracted light L- ₁ propagate in the light guide plate 1 in a state of total reflection and are emitted from the exit side diffraction grating 12, the light utilization efficiency is high.

[Embodiment 2]
(Configuration of the beam diameter expanding element 10)
FIG. 4 is an explanatory view showing an aspect of the light beam diameter expanding element 10 according to Embodiment 2 of the present invention. In FIG. 4, the left side of the drawing shows a state C31 in which the light beam diameter of the blue light L (B) is enlarged, and the right side of the drawing shows the light beam diameter of the red light L (R). A state C33 of enlargement is shown, and a state C32 of the light beam diameter of the green light L (G) is shown in the center of the drawing. FIG. 5 is an explanatory diagram when the blue light L (B) is incident on the blue light guide plate 1 (B) used in the light beam diameter expanding element 10 shown in FIG. FIG. 6 is an explanatory diagram when the green light L (G) is incident on the green light guide plate 1 (G) used in the light beam diameter expanding element 10 shown in FIG. FIG. 7 is an explanatory diagram when the red light L (R) is incident on the red light guide plate 1 (R) used in the light beam diameter enlarging element 10 shown in FIG. 5, 6, and 7, C41 (R), C41 (G), and C41 (B) are shown on the left side of the drawing when light having the shortest wavelength of each spectrum is incident. C42 (R), C42 (G), and C42 (B) are shown in the center toward the center when light having the longest wavelength of each spectrum is incident. C43 (R), C43 (G), and C43 (B) are shown in the case where the light with the longest wavelength is incident.

  As shown in FIG. 4, in the light beam diameter enlarging element 10 of the present embodiment, the blue light guide plate 1 (B), the green light guide plate 1 (G), Red light guide plates 1 (R) are sequentially arranged along the optical axis L. That is, each light guide plate 1 (R), 1 (G), 1 (B) is arranged in order from the shortest to the longest wavelength of the corresponding light. In this embodiment, the blue light guide plate 1 (B), the green light guide plate 1 (G), and the red light guide plate 1 (R) are each described with reference to FIGS. And substantially the same configuration. The light guide plates 1 (B), 1 (G), and 1 (R) have the same thickness.

  In the light beam diameter enlarging element 10 having such a configuration, the blue light L (B), the green light L (G), and the red light L (R) included in the image light are blue light guide plate 1 (B) and green light. The light guide plate 1 (G) and the red light guide plate 1 (R) are sequentially transmitted and emitted.

  In the light beam diameter expanding element 10 of this embodiment, the light guide plate 1 (B) includes one surface 1 a (B) and the other surface 1 b (B) facing the surface 1 a (B) in parallel. The incident side diffraction grating 11 (B) in which the grating 11a (B) extends in the x direction is provided on the surface 1a (B), and the grating 12a (B) extends in the x direction on the surface 1b (B). The existing exit side diffraction grating 12 (B) is provided. The incident side diffraction grating 11 (B) and the emission side diffraction grating 12 (B) have the same grating direction and grating period.

  The light guide plate 1 (G) is guided to the surface 1a (G) facing the surface 1b (B) of the light guide plate 1 (B) in parallel on the opposite side to the light guide plate 1 (B) and to the surface 1a (G). A surface 1b (G) facing in parallel on the opposite side to the optical plate 1 (B) is provided. An incident side diffraction grating 11 (G) in which a grating 11a (G) extends in the x direction is provided on the surface 1a (G), and a grating 12a (G) extends in the x direction on the surface 1b (G). An existing exit side diffraction grating 12 (G) is provided. The incident side diffraction grating 11 (G) and the emission side diffraction grating 12 (G) have the same grating direction and grating period. However, the incident-side diffraction grating 11 (G) and the emission-side diffraction grating 12 (G) have the same grating direction as the incident-side diffraction grating 11 (B) and the emission-side diffraction grating 12 (B), but the grating period is It is different.

  The light guide plate 1 (R) is guided to a surface 1a (R) facing the surface 1b (G) of the light guide plate 1 (G) in parallel on the opposite side to the light guide plate 1 (B) and to the surface 1a (R). A surface 1b (R) facing in parallel on the opposite side to the optical plate 1 (B) is provided. The incident side diffraction grating 11 (R) in which the grating 11a (R) extends in the x direction is provided on the surface 1a (R), and the grating 12a (R) extends in the x direction on the surface 1b (R). An existing exit-side diffraction grating 12 (R) is provided. The incident side diffraction grating 11 (R) and the emission side diffraction grating 12 (R) have the same grating direction and grating period. However, the incident side diffraction grating 11 (R) and the output side diffraction grating 12 (R) have the same grating direction as the incident side diffraction grating 11 (B) and the output side diffraction grating 12 (B), but the incident side diffraction grating The grating period is different from that of the grating 11 (B), the emitting side diffraction grating 12 (B), the incident side diffraction grating 11 (G), and the emitting side diffraction grating 12 (G).

In the light beam diameter enlarging element 10 configured as described above, the above-described constituent elements have the following relationship with the constituent elements in the present invention.
Light guide plate 1 (B) = first light guide plate surface 1 a (B) = first surface surface 1 b (B) = second surface incident side diffraction grating 11 (B) = first incident side diffraction grating output side diffraction grating 12 ( B) = first exit side diffraction grating Light guide plate 1 (G) = second light guide plate surface 1 a (G) = third surface surface 1 b (G) = fourth surface incident side diffraction grating 11 (G) = second incidence Side diffraction grating Output side diffraction grating 12 (G) = second output side diffraction grating Light guide plate 1 (R) = third light guide plate Surface 1 a (R) = Fifth surface Surface 1 b (R) = Sixth surface Incident side diffraction Grating 11 (R) = third incident side diffraction grating Emission side diffraction grating 12 (R) = third emission side diffraction grating Blue light L (B) = first light beam Green light L (G) = second light beam red light L (R) = third light ray

  In the light beam diameter enlarging element 10 of this embodiment, the incident angle with respect to the light guide plates 1 (B), 1 (G), 1 (R), the color of incident light, the grating period, the shortest wavelength of the corresponding color light, and the corresponding color light The longest wavelength, the + 1st order diffraction angle, and the −1st order diffraction angle are as shown in Table 2.

In this embodiment, as can be seen from Table 2, the grating period P1 of the incident side diffraction grating 11 (B) and the emission side diffraction grating 12 (B), and the incidence side diffraction grating 11 (G) and the emission side diffraction grating 12 (G ) And the grating period P3 of the incident side diffraction grating 11 (R) and the emission side diffraction grating 12 (R) are:
The following relationship is satisfied.
P1 <P2 <P3

Further, as described later, the grating height H11 of the incident side diffraction grating 11 (B), the grating height H12 of the emission side diffraction grating 12 (B), the grating height H21 of the incident side diffraction grating 11 (G), and the emission The grating height H22 of the side diffraction grating 12 (G), the grating height H31 of the incident side diffraction grating 11 (R), and the grating height H32 of the emission side diffraction grating 12 (R) satisfy the following relationship.
H11 <H21 <H31
H12 <H11
H22 <H21
H32 <H31
H12 <H11 <H22 <H21 <H32 <H31

In the light beam diameter enlarging element 10 of the present embodiment, as shown in FIGS. 4 and 5, the blue light guide plate 1 (B) has a blue wavelength band (blue light (with an incident angle of ± 7 °)). L (B) any of the + 1st order diffracted light _{L +1} and -1 order diffracted light _{L -1} for) also is diffracted at an angle greater than the critical angle of the light guide plate 1 (B), both from the incident position + y direction and -y direction The grating period P1 of the diffraction grating is set so that the diffracted light propagates through the light guide plate 1 (B).

  More specifically, the grating period P1 of the incident side diffraction grating 11 (B) and the emission side diffraction grating 12 (B) of the blue light guide plate 1 (B) is the shortest in the wavelength band of the blue light L (B). The first-order diffraction angle of the wavelength (λc = 0.45 μm) is set to 0.401 μm so as to be equal to the critical angle (37.6 °) of the light guide plate 1 (B) (refractive index = 1.64). . In FIG. 5, when the shortest wavelength (λcb = 0.45 μm) in the wavelength band of the blue light L (B) is incident on the blue light guide plate, the light beam of C41 (B) and the wavelength of the blue light L (B) When the longest wavelength (0.47 μm) in the band is incident on the light guide plate 1 (B) for blue, the light beam C42 (B) is shown. Further, FIG. 5 shows that when the shortest wavelength (λcb = 0.45 μm) in the wavelength band of the blue light L (B) is incident on the blue light guide plate 1 (B), the light beam C41 and the blue light L (B ) When the longest wavelength (0.47 μm) in the wavelength band is incident on the blue light guide plate 1 (B), the state of C43 (B) is shown when the light beam C42 is overlapped. As shown in FIG. 5, since there is no difference of 0.02 μm between the shortest wavelength and the longest wavelength in the wavelength band of the blue light L (B), the difference between the diffraction angles is small. Therefore, the difference between the light emission positions of the two is small.

  Further, as shown in FIG. 5, the grating height H11 of the incident side diffraction grating 11 (B) of the blue light guide plate 1 (B) is the shortest wavelength (λcb = 0) in the wavelength band of the blue light L (B). .45 μm) to the longest wavelength (0.47 μm), the first-order diffraction efficiency is set to be high. Further, the grating height H11 of the incident side diffraction grating 11 (B) has a higher first-order diffraction efficiency with respect to the blue light L (B) having a wavelength of 0.46 μm incident vertically, and the green light L incident vertically. The height is such that the diffraction efficiency for (G) and red light L (R) decreases. In this embodiment, the grating height H11 of the incident side diffraction grating 11 (B) is, for example, about 0.57 μm. Moreover, in the output side diffraction grating 12 (B), the light which has propagated through the light guide plate 1 (B) is emitted in a plurality of times. For this reason, if the first-order diffraction efficiency is high in the emission-side diffraction grating 12 (B), a lot of light is extracted by the first emission, and the amount of light is greatly attenuated from the next time. Therefore, the first-order diffraction efficiency of the exit-side diffraction grating 12 (B) is preferably lower than the first-order diffraction efficiency of the incident-side diffraction grating 11 (B). Therefore, in this embodiment, the grating height H12 of the output side diffraction grating 12 is lower than about 0.57 μm. Therefore, it is possible to optimize the light amount distribution emitted from the emission-side diffraction grating 12 (B).

  In the blue light guide plate 1 (B) configured as described above, the incident-side diffraction grating 11 (B) and the output-side diffraction grating 12 (B) have the same grating period P1, so that the light guide plate 1 (B) The light beam that has propagated through the total reflection and arrives at the output-side diffraction grating 12 (B) is emitted at the same angle as the incident angle. That is, the light emitted at the same angle as the incident angle is duplicated. The blue light guide plate 1 (B) also receives the green light L (G) and the red light L (R) at the same angle as the blue light L (B), but the green light L (G) and the red light. Since the wavelength of the light L (R) is longer than that of the blue light L (B), the light L (R) is diffracted at a larger angle than the blue light L (B).

  4 and 6, the blue light L (B), green light L (G), and red light L (R) emitted from the blue light guide plate 1 are incident on the blue light guide plate 1 (B). It is incident on the incident side diffraction grating 11 (G) of the green light guide plate 1 (G) at the same incident angle as the angle. In the green light guide plate 1 (G), both the + 1st order diffracted light and the −1st order diffracted light with respect to light in the green wavelength band with an incident angle in the range of ± 7 ° are larger than the critical angle of the light guide plate 1 (G). The grating period P2 of the diffraction grating is set so that the light is diffracted at an angle and the diffracted light propagates in the light guide plate 1 (G) in both the + y direction and the −y direction from the incident position.

  More specifically, the grating period P2 of the incident side diffraction grating 11 (G) and the emission side diffraction grating 12 (G) of the green light guide plate 1 (G) is the shortest in the wavelength band of the green light L (G). The first diffraction angle of the wavelength (λcg = 0.52 μm) is set to 0.464 μm so as to be equal to the critical angle (37.6 °) of the light guide plate (refractive index = 1.64). In FIG. 6, when the shortest wavelength (λcg = 0.52 μm) in the wavelength band of the green light L (G) is incident on the green light guide plate 1 (G), the light of C41 (G) and the green light L ( When the longest wavelength (0.54 μm) in the wavelength band G) is incident on the green light guide plate 1 (G), the light beam C42 (G) is shown. Further, FIG. 6 shows the light of C41 (G) and the green light when the shortest wavelength (λcg = 0.52 μm) in the wavelength band of the green light L (G) is incident on the green light guide plate 1 (G). When the longest wavelength (0.54 μm) in the wavelength band is incident on the light guide plate for green, the state of C43 (G) is shown when the light of C42 (G) is overlapped. As shown in FIG. 6, since there is no difference of 0.02 μm between the shortest wavelength and the longest wavelength in the wavelength band of the green light L (G), the difference between the diffraction angles is small. Therefore, the difference between the light emission positions of the two is small.

  As shown in FIG. 6, the grating height H21 of the incident side diffraction grating 11 (G) of the green light guide plate 1 (G) is the shortest wavelength (λcg = 0) in the wavelength band of the green light L (G). .52 μm) to the longest wavelength (0.54 μm), the first-order diffraction efficiency is set to be high. In this embodiment, the grating height H21 of the incident-side diffraction grating 11 (G) has a higher first-order diffraction efficiency for green light L (G) having a wavelength of 0.52 μm that is incident vertically, and blue light that is incident vertically. The diffraction efficiency for light L (B) and red light L (R) is low. In this embodiment, the grating height H21 of the incident side diffraction grating 11 (G) is, for example, about 0.60 μm. In addition, since the first-order diffraction efficiency of the output-side diffraction grating is preferably lower than the first-order diffraction efficiency of the input-side diffraction grating, the grating height H22 of the output-side diffraction grating 12 (R) is about 0.60 μm. Low. Therefore, the light quantity distribution emitted from the emission side diffraction grating 12 (G) can be optimized.

  In the green light guide plate 1 (G) configured as described above, since the incident side diffraction grating 11 (G) and the output side diffraction grating 12 (G) have the same grating period P2, the light guide plate 1 (G) The light beam that has propagated through the total reflection and arrives at the output-side diffraction grating 12 (G) is emitted at the same angle as the incident angle. Therefore, the light emitted at the same angle as the incident angle is duplicated.

  4 and 7, the blue light L (B), the green light L (G), and the red light L (R) emitted from the green light guide plate 1 (B) are blue light guide plate 1 (B ) With respect to the incident side diffraction grating 11 (R) of the red light guide plate 1 (R). In the red light guide plate 1 (R), both the + 1st order diffracted light and the −1st order diffracted light with respect to light in the red wavelength band with an incident angle in the range of ± 7 ° are larger than the critical angle of the light guide plate 1 (R). The grating period of the diffraction grating is set so that the light is diffracted at an angle and diffracted light propagates in the light guide plate 1 (R) in both the + y direction and the −y direction from the incident position.

  More specifically, the grating period P3 of the incident side diffraction grating 11 (R) and the emission side diffraction grating 12 (R) of the red light guide plate 1 (R) is the shortest in the wavelength band of the red light L (R). The first-order diffraction angle of the wavelength (λcr = 0.60 μm) is set to 0.535 μm so as to be equal to the critical angle (37.6 °) of the light guide plate 1 (R) (refractive index = 1.64). . In FIG. 7, when the shortest wavelength (λcr = 0.60 μm) in the wavelength band of the red light L (R) is incident on the red light guide plate 1 (R), the light beam C41 (R) and the red light L ( When the longest wavelength (0.62 μm) in the wavelength band R) is incident on the red light guide plate 1 (R), the light beam C42 (R) is shown. Further, FIG. 7 shows the light of C41 (R) and the red light when the shortest wavelength (λcr = 0.60 μm) in the wavelength band of the red light L (R) is incident on the red light guide plate 1 (R). When the longest wavelength (0.62 μm) in the wavelength band of L (R) is incident on the red light guide plate 1 (R), the state of C43 (R) is shown when the light of C42 (R) is superimposed. . As shown in FIG. 6, since there is no difference of 0.02 μm between the shortest wavelength and the longest wavelength in the wavelength band of the red light L (R), the difference between the diffraction angles is small. Therefore, the difference between the light emission positions of the two is small.

  Further, the grating height H31 of the incident side diffraction grating 11 (R) of the red light guide plate 1 (R) is from the shortest wavelength (λcr = 0.60 μm) to the longest wavelength in the wavelength band of the red light L (R). The first-order diffraction efficiency is set to be high in the range of 0.62 μm). In this embodiment, the grating height H31 of the incident-side diffraction grating 11 (R) has a higher first-order diffraction efficiency for red light having a wavelength of 0.60 μm that is incident vertically, and blue light or green light that is incident vertically. The height at which the diffraction efficiency with respect to is low. In this embodiment, the grating height H31 of the incident side diffraction grating 11 (R) is about 0.70 μm. Further, since the first-order diffraction efficiency of the exit-side diffraction grating 12 (R) is preferably lower than the first-order diffraction efficiency of the entrance-side diffraction grating 11 (R), the grating height of the exit-side diffraction grating 12 (R) H32 is lower than about 0.70 μm. Therefore, it is possible to optimize the light amount distribution emitted from the emission side diffraction grating 12 (R).

  In the red light guide plate 1 (R) configured as described above, the incident side diffraction grating 11 (R) and the output side diffraction grating 12 (R) have the same grating period P3. Then, the light beam that has propagated through the total reflection and reaches the output-side diffraction grating 12 (R) is emitted at the same angle as the incident angle. Therefore, the light emitted at the same angle as the incident angle is duplicated. At that time, the diffraction grating of the red light guide plate 1 (R) is set so that the diffraction efficiency becomes high at the wavelength of the red light L (R), so the blue light L (B) and Low diffraction efficiency for green light (LG). Therefore, the influence of unnecessary diffracted light can be suppressed.

  In the light beam diameter expanding element 10 of this embodiment, the blue light L (B), the green light L (G), and the red light L (R) emitted from the blue light guide plate 1 (B) are emitted from the green light guide plate 1. (G) and red light guide plate 1 (R) are sequentially incident and diffracted by the diffraction grating provided on these light guide plates. The blue light L (B), green light L (G), and red light L (R) emitted from the green light guide plate 1 (G) are red light guide plate 1 (R) and red light guide. The light enters the optical plate 1 (R) and is diffracted by the diffraction grating provided on these light guide plates. At that time, the green light guide plate 1 (G) and the red light guide plate 1 (R) emit unnecessary diffracted light other than the required angle. Even in such a case, if the diffraction angle of unnecessary diffracted light is sufficiently larger than 7 °, it can be shielded or absorbed later.

(Main effects of this form)
As described above, in the light beam diameter enlarging element 10 of the present embodiment, the light guide plates 1 (B), 1 (G), and 1 (R) each have the configuration described in the first embodiment. The light beam diameter is emitted in a sufficiently expanded state. Therefore, it is possible to suppress an increase in the size of the light beam diameter expanding element, and the light use efficiency is high. In addition, in the blue light guide plate 1 (B), the green light guide plate 1 (G), and the red light guide plate 1 (R), the lattice period is set as described above, so that each light guide plate 1 (B ) In 1 (G) and 1 (R), the angle of the light beam propagating in the light guide plate can be set to be the same. Therefore, if the light guide plates 1 (B), 1 (G), and 1 (R have the same thickness, the blue light L (B), the green light L (G), and the red light emitted from the light beam diameter expanding element Since the intervals between the light beams in the light L (R) can be made the same, it is possible to make the light quantity distribution of the emitted light of each color uniform, thus suppressing the occurrence of color unevenness in the emitted light beam. Since the optical plates 1 (R), 1 (G), and 1 (B) are arranged in the order of the corresponding wavelengths of light from shortest to longest, generation of unnecessary diffracted light can be suppressed.

  In addition, in blue light, green light, and red light, the spectral range of 0.02 μm is, for example. This can be realized by inserting a band-pass filter between a liquid crystal device described later and an LED as a light source. When an organic electroluminescence device is used, the above spectral range can be realized by providing a micro optical resonator structure in the organic electroluminescence element.

[Embodiment 3]
FIG. 8 is an explanatory view showing one aspect of the light beam diameter expanding element 10 according to Embodiment 3 of the present invention. In FIG. 8, the left side of the drawing shows a state C51 in which the light beam diameter of the red light L (R) is enlarged, and the right side of the drawing shows the light beam diameter of the blue light L (B). An enlarged state C53 is shown, and in the center of the drawing, a state C52 in which the light beam diameter of the green light L (G) is enlarged is shown. In addition, since the basic configuration of this embodiment is the same as that of the second embodiment, common portions are denoted by the same reference numerals and description thereof is omitted.

  In the light beam diameter enlarging element 10 according to the second embodiment, the blue light guide plate 1 (B), the green light guide plate 1 (G), and the red light guide plate are arranged from the image light incident side to the light emitting side. The light guide plate 1 (R) was sequentially arranged along the optical axis L. On the other hand, in the light beam diameter enlarging element 10 of this embodiment, as shown in FIG. 8, the red light guide plate 1 (R) and the green light guide plate 1 from the incident side to the outgoing side of the image light. (G) and the light guide plate 1 (B) for blue are arranged in order along the optical axis L. That is, each light guide plate 1 (R), 1 (G), 1 (B) is arranged in order from the longest wavelength of the corresponding light.

Therefore, each component of the light beam diameter expanding element 10 of this embodiment has the following relationship with the component in the present invention.
Light guide plate 1 (R) = first light guide plate surface 1 a (R) = first surface surface 1 b (R) = second surface incident side diffraction grating 11 (R) = first incident side diffraction grating output side diffraction grating 12 ( R) = first exit side diffraction grating Light guide plate 1 (G) = second light guide plate surface 1 a (G) = third surface surface 1 b (G) = fourth surface incident side diffraction grating 11 (G) = second incidence Side diffraction grating Output side diffraction grating 12 (G) = second output side diffraction grating Light guide plate 1 (B) = third light guide plate surface 1 a (B) = fifth surface surface 1 b (B) = sixth surface incident side diffraction Grating 11 (B) = third incident side diffraction grating Emission side diffraction grating 12 (B) = third emission side diffraction grating Red light L (R) = first light beam Green light L (G) = second light beam blue light L (B) = 3rd ray

  The other configuration has the same configuration as the light guide plate described with reference to FIG. This light beam diameter enlarging element 10 also has the same effects as in the second embodiment, such as being able to align the light quantity distribution of the emitted light of each color, as with the light beam diameter enlarging element 10 according to the second embodiment.

[Embodiment 4]
FIG. 9 is an explanatory diagram showing a configuration example of a display device including the light beam diameter expanding element 10 to which the present invention is applied. FIG. 10 is an explanatory diagram showing an optical system of the display device shown in FIG. FIG. 11 is an explanatory diagram of the exit pupil of the optical system shown in FIG.

  A display device 100 shown in FIG. 9 is a head-mounted display (head-mounted display device) having an appearance like glasses. The display device 100 can cause the observer wearing the display device 100 to recognize the image light, and can allow the observer to observe the outside world image in a see-through manner. The display device 100 includes an optical panel 110 that covers the front of the viewer's eyes, a frame 121 that supports the optical panel 110, and a first drive unit 131 and a second drive unit 132 that are provided on a side frame of the frame 121. Yes. The optical panel 110 has a first panel portion 111 and a second panel portion 112, and the first panel portion 111 and the second panel portion 112 are plate-like parts integrally connected at the center. It has become. The first display device 100A in which the first panel portion 111 and the first drive unit 131 on the left side in the drawing are combined is a portion for the left eye, and functions alone as a virtual image display device. Further, the second display device 100B in which the second panel portion 112 on the right side and the second drive unit 132 in the drawing are combined is a right eye portion, and functions alone as a virtual image display device.

  Here, since the second display device 100B has the same structure as the first display device 100A and has a configuration in which left and right are reversed, the following description will focus on the first display device 100A. A detailed description of the two-display device 100B is omitted.

  As shown in FIG. 10, the first display device 100 </ b> A includes an image light projection device 15 and a light guide optical device 20. The image light projection device 15 corresponds to the first drive unit 131 in FIG. 3, and the light guide optical device 20 corresponds to the first panel portion 111 in FIG. In the second display device 100B shown in FIG. 9, the image light projection device 15 corresponds to the second drive unit 132, and the light guide optical device 20 corresponds to the second panel portion 112.

  The image light projector 15 includes an image forming device 16 and a projection optical system 17. Although not shown, the image forming apparatus 16 includes an illumination device that emits two-dimensional illumination light, a transmissive liquid crystal display device, and a drive control unit that controls operations of the illumination device and the liquid crystal display device. . The illuminating device generates light including three colors of red, green, and blue, and the liquid crystal display device spatially modulates the illuminating light from the illuminating device to generate image light L1 to be a display target such as a moving image. Form.

  In this embodiment, the projection optical system 17 includes a collimator lens 18 having a power for condensing the light beam of the image light L1 emitted from each point on the image forming apparatus 16 (liquid crystal display device). The image forming apparatus 16 may be a reflective spatial light modulator that reflects light from a light source with a mirror such as a MEMS to form an image, or an organic electroluminescence display element.

  The light guide optical device 20 includes an irradiated region 21 to which the image light L1 is irradiated, and a display light emitting region 23 that emits the light that has entered the irradiated region 21 and traveled as display light L2.

  In the present embodiment, the light guide optical device 20 guides the light beam diameter expanding element 10 and the image light L1 emitted from the light beam diameter expanding element 10 in the x direction (second direction) intersecting the y direction (first direction). And a light guide optical system 25. The light beam diameter expanding element 10 is a light beam diameter expanding element to which the present invention is applied, and has, for example, the configuration described with reference to the second embodiment. The light guide optical system 25 has a light guide plate 30 extending in the x direction. The light guide plate 30 includes an incident side diffraction grating 31 that faces the light beam diameter enlarging element 10 at one end portion in the x direction and an emission side diffraction grating 32 that faces the eye E at the other end portion in the x direction. The display light emission region 23 is constituted by the emission side diffraction grating 32.

  Here, the size of the light beam diameter expanding element 10 in the y direction is smaller than the size of the light guide optical system 25 (light guide plate 30) in the y direction. For this reason, the light beam diameter enlarging element 10 does not protrude in the y direction from the light guide optical system 25 (light guide plate 30).

In this embodiment, the y direction (first direction) corresponds to the vertical direction, and in the light beam diameter expanding element 10, three light guide plates (blue light guide plate 1 (B) and green light guide plate 1 (G) are provided. , And red light guide plate 1 (R), respectively, extend in the vertical direction (y direction). Each of the three light guide plates (blue light guide plate 1 (B), green light guide plate 1 (G), and red light guide plate 1 (R)) has a lattice extending in the x direction. Incident-side diffraction gratings 11 (B), 11 (G), and 11 (R) and output-side diffraction gratings 12 (B), 12 (G), and 12 (R) that extend in the x direction are provided. ing.
Accordingly, the image light L1 emitted from the image light projector 15 is incident on the light beam diameter enlarging element 10, and after the light beam diameter is expanded in the vertical direction (y direction) by the light beam diameter enlarging element 10, the light guide plate 30. To the incident side diffraction grating 31. The light incident from the incident side diffraction grating 31 of the light guide plate 30 propagates in the light guide plate 30 in the x direction (second direction), and is emitted from the emission side diffraction grating 32 of the light guide plate 30 toward the eye E. During this period, the pupil is magnified in the horizontal direction (x direction).

  Here, in the image light projection device 15, as shown in FIG. 11, the image light emitted from the image forming device 16 is converted into parallel light by the collimator lens 18 of the projection optical system 17. Here, the exit pupil 170 of the projection optical system 17 has an incident surface (surface 1a (B) of the blue light guide plate 1 (B)) and the light beam diameter expanding element 10 in the optical axis direction. It is located between the exit surface (the surface 1b (R) of the red light guide plate 1 (R). In this embodiment, the exit pupil 170 of the projection optical system 17 is the surface of the green light guide plate 1 (G). For this reason, the light guide plate 1 (B) for blue, the light guide plate 1 (G) for green, and the light guide plate 1 (G) for green, each of which uses the light of all the field angles of the image light L1 for the light beam diameter expanding element 10, The red light guide plate 1 (R) can be incident on the incident-side diffraction gratings 11 (B), (G), and (R), so that the blue light L (B) and the green light L are spread over the entire screen. Images of all colors of (G) and red light L (R) can be displayed, and the exit pupil 170 of the projection optical system 17 can be displayed. In the optical axis direction, the incident surface (surface 1a (B) of the blue light guide plate 1 (B)) and the exit surface (red light guide plate 1 (R) of the light beam diameter expanding device 10) of the light beam diameter expanding device 10. The light guide plate 1 (B) for blue light using all the angles of view of the image light L1 for the light beam diameter expanding element 10 is preferably disposed in the middle of the surface 1b (R). The light can be reliably incident on the incident-side diffraction gratings 11 (B), (G), and (R) of the green light guide plate 1 (G) and the red light guide plate 1 (R). In addition, the images of all the colors of the blue light L (B), the green light L (G), and the red light L (R) can be more reliably displayed.

[Embodiment 5]
FIG. 12 is an explanatory diagram showing another configuration example of the display device including the light beam diameter enlarging element 10 to which the present invention is applied. Since the basic configuration of this embodiment is the same as that of Embodiment 4, common portions are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 12, the first display device 100 </ b> A of the present embodiment also includes an image forming device 16 and a projection optical system 17 as in the fourth embodiment. The light guide optical device 20 includes a light beam diameter expanding element 10 and a light guide optical system that guides the image light L1 emitted from the light beam diameter expanding element 10 in the x direction (second direction) intersecting the y direction (first direction). 25. The light beam diameter expanding element 10 is a light beam diameter expanding element to which the present invention is applied, and has, for example, the configuration described with reference to the second embodiment. The light guide optical system 25 has a light guide plate 30 extending in the x direction. Here, the size of the light beam diameter expanding element 10 in the y direction is smaller than the size of the light guide optical system 25 (light guide plate 30) in the y direction. For this reason, the light beam diameter enlarging element 10 does not protrude in the y direction from the light guide optical system 25 (light guide plate 30).

In this embodiment, the y direction (first direction) corresponds to the lateral direction, and in the light beam diameter expanding element 10, three light guide plates (blue light guide plate 1 (B) and green light guide plate 1 (G) are provided. , And red light guide plate 1 (R), respectively, extend in the lateral direction (y direction). The x direction (second direction) corresponds to the vertical direction, and the light guide plate 30 extends in the vertical direction (x direction).
Also in the first display device 100A configured as described above, the image light L1 emitted from the image light projection device 15 is incident on the light beam diameter expansion element 10 and is emitted by the light beam diameter expansion element 10 as in the fourth embodiment. After the beam diameter is enlarged in the vertical direction (y direction), the light beam is emitted to the incident side diffraction grating 31 of the light guide plate 30. The light incident from the incident side diffraction grating 31 of the light guide plate 30 propagates in the light guide plate 30 in the x direction (second direction), and is emitted from the emission side diffraction grating 32 of the light guide plate 30 toward the eye E. During this period, the pupil is magnified in the horizontal direction (x direction).

[Other embodiments]
In the second, third, fourth, and fifth embodiments, the light beam diameter expanding element 10 has three light guide plates. However, a configuration having two light guide plates may be employed. In this case, for example, one of the two light guide plates enlarges the light beam diameter of the blue light L (B) and the green light L (G), and the other light beam of the red light L (R). Increase the diameter.

1, 1 (B), 1 (G), 1 (R) ... light guide plate, 1 a, 1 a (B), 1 a (G), 1 a (R) ... surface, 1 b, 1 b (B), 1 b (G) DESCRIPTION OF SYMBOLS 1b (R) ... surface, 10 ... Light beam diameter expansion element 11, 11 (B), 11 (G), 11 (R) ... Incident side diffraction grating, 11a, 11a (B), 11a (G), 11a (R) ... grating, 12, 12 (B), 12 (G), 12 (R) ... exit side diffraction grating, 12a, 12a (B), 12a (G), 12a (R) ... grating, 15 ... image Optical projection device, 16 ... image forming device, 17 ... projection optical system, 18 ... collimator lens, 20 ... light guide optical device, 21 ... irradiated region, 23 ... display light emitting region, 25 ... light guide optical system, 30 DESCRIPTION OF SYMBOLS ... Light guide plate, 31 ... Incident side diffraction grating, 32 ... Outgoing side diffraction grating, 100 ... Display apparatus, 100A ... First display apparatus, 100B ... Second display 110, optical panel, 111, first panel portion, 112, second panel portion, 121, frame, 131, first drive unit, 132, second drive unit, 170, exit pupil, E, eye, L,. Optical axis, L0 ... 0th order diffracted light, L _{+ 1} ... + 1st order diffracted light, L- ₁ ...- 1st order diffracted light, L1 ... Image light, L2 ... Display light, L10 ... Light ray L (B) ... Blue light, L (G) ... green light, L (R) ... red light, P ... lattice period, P1 ... lattice period, P2 ... lattice period, P3 ... lattice period

Claims (10)

A first light guide plate having a first surface and a second surface which is a surface opposite to the first surface;
A first incident-side diffraction grating provided on the first surface;
A first exit-side diffraction grating provided on the second surface;
A second light guide plate provided with a third surface facing the second surface of the first light guide plate, and having a fourth surface on the opposite side of the third surface;
A second incident side diffraction grating provided on the third surface;
A second exit-side diffraction grating provided on the fourth surface;
A third light guide plate provided with a fifth surface facing the fourth surface of the second light guide plate, and having a sixth surface on the opposite side of the fifth surface;
A third incident-side diffraction grating provided on the fifth surface;
A third exit-side diffraction grating provided on the sixth surface;
Have
The first surface is provided to be parallel to the second surface,
The first incident-side diffraction grating and the first emission-side diffraction grating are provided so that the grating direction is the same direction and the grating period is the same period,
The refractive index of the first light guide plate is such that the diffraction angle of the + 1st order diffracted light and the diffraction angle of the −1st order diffracted light of the first light incident on the first incident-side diffraction grating are equal to or greater than the critical angle, respectively. Is the refractive index,
When the direction intersecting the grating direction of the first incident side diffraction grating is the first direction,
The + 1st order diffracted light and the −1st order diffracted light of the first light beam diffracted by the first incident side diffraction grating are propagated in the first light guide plate in directions opposite to each other in the first direction. Emitted from the side diffraction grating ,
The third surface is provided to be parallel to the fourth surface,
The second incident side diffraction grating and the second emission side diffraction grating are provided such that the grating direction is the same direction and the grating period is the same period,
The grating direction of the second incident side diffraction grating is provided to be the same direction as the grating direction of the first incident side diffraction grating,
The grating period of the second incident side diffraction grating is provided to be different from the grating period of the first incident side diffraction grating,
The refractive index of the second light guide plate is such that the second light beam having a wavelength different from that of the first light beam is incident on the second incident-side diffraction grating, the diffraction angle of the + 1st order diffracted light of the second light beam, and the −1st order diffracted light. Is a refractive index such that the diffraction angle of each becomes an angle greater than the critical angle,
The + 1st order diffracted light and the −1st order diffracted light of the second light beam diffracted by the second incident side diffraction grating propagate in the second light guide plate in directions opposite to each other in the first direction, and the second emission. Emitted from the side diffraction grating,
The fifth surface is provided to be parallel to the sixth surface,
The third incident side diffraction grating and the third emission side diffraction grating are provided such that the grating directions are the same direction and the grating period is the same period,
The grating direction of the third incident side diffraction grating is provided to be the same direction as the grating direction of the first incident side diffraction grating,
The grating period of the third incident side diffraction grating is provided to be different from the grating period of the first incident side diffraction grating and the second incident side diffraction grating,
The refractive index of the third light guide plate is a diffraction angle of the + 1st order diffracted light of the third light beam when a third light beam having a wavelength different from that of the first light beam and the second light beam is incident on the third incident side diffraction grating. And the refractive index so that the diffraction angles of the -1st order diffracted light are each greater than the critical angle,
The + 1st order diffracted light and the −1st order diffracted light of the third light beam diffracted by the third incident side diffraction grating propagate in the third light guide plate in directions opposite to each other in the first direction, and the third emission. Emitted from the side diffraction grating,
The grating height of the first incident side diffraction grating is H11,
The grating height of the second incident side diffraction grating is H21,
When the grating height of the third incident side diffraction grating is H31,
The lattice heights H11, H21, and H31 have the following relationship:
H11 <H21 <H31
Beam diameter enlarging element characterized that you have met the. In the light beam diameter expanding element according to claim 1 ,
The grating period of the first incident side diffraction grating is P1,
The grating period of the second incident side diffraction grating is P2,
When the grating period of the third incident side diffraction grating is P3,
The lattice periods P1, P2, and P3 have the following relationship: P1 <P2 <P3
A light beam diameter enlarging element characterized by satisfying In the light beam diameter expanding element according to claim 1 or 2 ,
The grating height of the first output side diffraction grating is H12,
The grating height of the second exit side diffraction grating is H22,
When the grating height of the third output side diffraction grating is H32,
The lattice heights H11, H12, H21, H22, H31, and H32 have the following relationship: H12 <H11 <H22 <H21 <H32 <H31
A light beam diameter enlarging element characterized by satisfying   A first light guide plate having a first surface and a second surface which is a surface opposite to the first surface;
  A first incident-side diffraction grating provided on the first surface;
  A first exit-side diffraction grating provided on the second surface;
  A second light guide plate provided with a third surface facing the second surface of the first light guide plate, and having a fourth surface on the opposite side of the third surface;
  A second incident side diffraction grating provided on the third surface;
  A second exit-side diffraction grating provided on the fourth surface;
  Have
  The first surface is provided to be parallel to the second surface,
  The first incident side diffraction grating and the first emission side diffraction grating are provided so that the grating directions are the same direction and the grating period is the same period,
  The refractive index of the first light guide plate is such that the diffraction angle of the + 1st order diffracted light and the diffraction angle of the −1st order diffracted light incident on the first incident-side diffraction grating are equal to or greater than the critical angle, respectively. Is the refractive index,
  When the direction intersecting the grating direction of the first incident side diffraction grating is the first direction,
  The + 1st order diffracted light and the −1st order diffracted light of the first light beam diffracted by the first incident side diffraction grating are propagated in the first light guide plate in directions opposite to each other in the first direction. Emitted from the side diffraction grating,
  The third surface is provided to be parallel to the fourth surface,
  The second incident side diffraction grating and the second emission side diffraction grating are provided such that the grating directions are the same direction and the grating period is the same period,
  The grating direction of the second incident side diffraction grating is provided to be the same direction as the grating direction of the first incident side diffraction grating,
  The grating period of the second incident side diffraction grating is provided to be different from the grating period of the first incident side diffraction grating,
  The refractive index of the second light guide plate is such that the second light beam having a wavelength different from that of the first light beam is incident on the second incident-side diffraction grating, the diffraction angle of the + 1st order diffracted light of the second light beam, and the −1st order diffracted light. Is a refractive index such that the diffraction angle of each becomes an angle greater than the critical angle,
  The + 1st order diffracted light and the −1st order diffracted light of the second light beam diffracted by the second incident side diffraction grating propagate in the second light guide plate in directions opposite to each other in the first direction. Emitted from the side diffraction grating,
  The grating height of the first incident side diffraction grating is H11,
  When the grating height of the second incident side diffraction grating is H21,
  The lattice heights H11 and H21 have the following relationship:
      H11 <H21
A light beam diameter enlarging element characterized by satisfying In the light flux diameter enlarging element according to any one of claims 1 to 4 ,
The grating period of the first incident side diffraction grating and the first emission side diffraction grating is P,
The shortest wavelength in the half width of the spectrum of the first light is λc,
When the maximum incident angle of the first light beam with respect to the first incident side diffraction grating is θmax,
The grating period P, the shortest wavelength λc, and the maximum incident angle θmax have the following relationship: P ≦ λc / [sin (θmax) +1]
A light beam diameter enlarging element characterized by satisfying A first light guide plate having a first surface and a second surface which is a surface opposite to the first surface;
A first incident-side diffraction grating provided on the first surface;
A first exit-side diffraction grating provided on the second surface;
An image light projection device comprising an image generation device and a collimator lens, and causing the image light generated by the image generation device to enter the light beam diameter enlarging element through the collimator lens;
A light guide optical system that guides image light emitted from the light beam diameter enlarging element in a second direction intersecting the first direction;
Have
The first surface is provided to be parallel to the second surface,
The first incident side diffraction grating and the first emission side diffraction grating are provided so that the grating directions are the same direction and the grating period is the same period,
The refractive index of the first light guide plate is such that the diffraction angle of the + 1st order diffracted light and the diffraction angle of the −1st order diffracted light incident on the first incident-side diffraction grating are equal to or greater than the critical angle, respectively. Is the refractive index,
When the direction intersecting the grating direction of the first incident side diffraction grating is the first direction,
The + 1st order diffracted light and the −1st order diffracted light of the first light beam diffracted by the first incident side diffraction grating are propagated in the first light guide plate in directions opposite to each other in the first direction. Emitted from the side diffraction grating,
A display device, wherein an exit pupil in the image light projection device is located between an entrance surface and an exit surface of the light beam diameter enlarging element . The display device according to claim 6 ,
The display apparatus, wherein the exit pupil is located between an entrance surface and an exit surface of the light beam diameter enlarging element. The display device according to claim 6 or 7 ,
The display device, wherein a size of the light beam diameter enlarging element in the first direction is smaller than a size of the light guide optical system in the first direction. The display device according to any one of claims 6 to 8 ,
The first direction is a vertical direction when viewed from an observer observing the image light ,
The display device according to claim 1, wherein the second direction is a horizontal direction when viewed from an observer who observes the image light . The display device according to any one of claims 6 to 8 ,
The first direction is a side direction as viewed from an observer observing the image light ,
The display device characterized in that the second direction is a vertical direction as viewed from an observer who observes the image light .

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